[Beatles]

Is somebody of you a good analytic chemists?
I'm staring having anal.-laboratory this turm, and I need some help with ion detections!

Pls Help

[Alberto_Kravina]

Hello Beatles!

Analytical chemistry is my strong point.
My speciallity is anion and cation analysis...

so it you need help for school just ask me.

PS: What are you doing at the moment in the lab at school?

[Beatles]

Hey Alberto Thank a lot!!!!!

We have started with Cl-, SO42- and I- detections.

My question: do you have any suggestions for this detection reactions?

[Alberto_Kravina]

You have to explain how you detect this ions, I mean, there is not only one way to determine chloride and iodide

[Beatles]

We detect Iodide with hypochlorite and chloroform, cloride with silver nitrate and sulfate with Bacl2.

any suggestions?

[Alberto_Kravina]

Well....there's nothing special to suggest for the sulfate detection, just add barium chloride.
You have to check for carbonates before, because if there's carbonate you'll also obtain a white precipitate.
If there's carbonate just add a bit of HCl: CO₃^2- + 2 H⁺ ---> CO₂ + H₂O

after that just add BaCl₂ => White ppt shows sulfate

For Chloride..just add silver nitrate (pH should be about 5-6)
=>White, cheese-like ppt shows chloride.
Ag⁺ + Cl^-------> AgCl(s)

Hint: AgCl decomposes with light to blue-gray silver and chlorine.

2 AgCl ------Light--------> 2 Ag(s) + Cl_2(g)

For Iodide:

If it doesn't work with Chloroform try with Carbon tetrachloride (CCl₄)

Another thing that you can do is making a fresh chlorine solution (with MnO₂ and HCl).

Cl₂ + H₂O ----> HOCl + HCl

[Beatles]

Hey Thanks a lot! any other suggestions from other people?

[skyaintsnow]

Hi beatles,

I don't really know what your problem is. Do you have course lab manual to refer to, and just follow the procedures or do you have to plan the experiment yourself?
 
If you only need to qualitatively determine if these ions are present in the solution, alberto has given a lot of information. If you need to determine the concentration as well, I'd say you may need to do some titrations or anion chromatography. For Cl- and SO42- the metod is called precipitation titration, in which you might use autotitrator. Not sure about I- though.